1. Technical Field
The present invention relates to telescopically expandable guards for covering coupled rotating shafts.
2. Description of the Related Art
Power drive lines, such as the power take-off shaft of a mobile prime mover, a tractor for example, and the power input shaft of an attached implement, a mower deck for example, can have rotating shafts and other components that would be exposed to the surrounding environment unless shielded in some way. Exposed rotating components are a hazard and are susceptible to damage if interfered with. Fixed covers and guards are typically used to partially or fully encase these components.
Often, however, the mating components pivot or translate relative to each other during operation, such as is the case of a power field implement, coupled to the power take-off shaft of a tractor. The mating components are thus often coupled with telescoping shafts and one or more universal joints may be used to provide an articulated coupling accommodating this movement and any angular misalignment that may exist.
Guards for telescopically coupled shafts and universal joints are well known, see e.g. U.S. Pat. Nos. 3,031,865; 3,113,441 and 4,605,332. Prior art guards are usually provided in two halves. One half of the guard can be axially fixed or journaled upon a rotating member of the drive line and the other half can be stationary, being fixed to either the prime mover or to the implement. Or, both of the guard sections can be freely rotatable upon their respective shaft sections. In either case, the guard covers the rotating shafts and has smooth external surfaces that do not readily grab fingers, clothing, etc. If the guard rotates, there is usually such low friction between the guard and the shafts that the guard will come to rest if contacted without impeding the rotation of the shafts.
Typically one or both of the two guard sections are shorter than the length of the associated shaft so that at least one of the mating ends of the shafts are visible for coupling and also so that the shafts can be coupled fully without interference from the guard. Despite being shorter than the shafts, when the shafts are coupled fully the guard sections overlap and cover both shafts. However, in extreme situations in which the shafts are pulled apart so as to be near disengagement, the guard sections can separate and expose the rotating shafts, thereby rendering the guard at least partially ineffective.
An improved telescopic guard for shielding coupled rotating shafts is therefore needed.